Tadpole trike with front hub motor

[mmiller50]

I hope that this is in the right place- apologies if not. Also this topic may have been covered elsewhere but I couldn’t find much information that I could use.
I have a Greenspeed GT20 which I electrified using. A Grin All Axle motor at the rear. This has been successful in that I rode it this summer from just south of Paris to the Cote d’Azur over 10 days. Over 10 days with an average of 75-80 miles ( more or less on one charge) - it was a blast! However I am not a fan of derailleur gears so have decided to put a Rohloff hub on the back and power one of the front wheels. To this end I have a Grin front All Axle but what I didn’t factor in is that the axle on the Greenspeed is not long enough to accommodate the motor ( it needs to be approximately twice as long).
When I discovered this I ( belatedly) realised that I should have put more foresight into the project..! Given that I am unlikely to find an off the peg solution to the Greenspeed axle nor do I have the resources to have a new axle/ kingpin made up - so what to do?
I have noticed that the Greenspeed axle has an internal thread so I did think that I could add an extension to the axle connecting the two parts by an internal screw and thus proceed that way. Is this a mad idea( it seems as if it could work as long as the two pieces of axle were correctly aligned) but maybe I am missing something obvious? If this can’t be made to work I will either have to revert to the previous setup ( and live with my dislike of derailleur gearing) or alternatively use a mid- drive motor at the crank. I had this setup on my KingCycle which worked well but I just think that the Grin AllAxle is a superb motor so I am reluctant to give up quite yet. Any views, help will be gratefully received!

 

[PaPaSteve]

Not knowing any details about a Greenspeed trike it does sound like purchasing a longer bolt is a possible solution to mount the motor.
However, driving just one front wheel will cause torque steer.
While it may be controllable, after a while it will become tiring keeping it going straight.

 

[qwerkus]

I hope that this is in the right place- apologies if not. Also this topic may have been covered elsewhere but I couldn’t find much information that I could use.
I have a Greenspeed GT20 which I electrified using. A Grin All Axle motor at the rear. This has been successful in that I rode it this summer from just south of Paris to the Cote d’Azur over 10 days. Over 10 days with an average of 75-80 miles ( more or less on one charge) - it was a blast! However I am not a fan of derailleur gears so have decided to put a Rohloff hub on the back and power one of the front wheels. To this end I have a Grin front All Axle but what I didn’t factor in is that the axle on the Greenspeed is not long enough to accommodate the motor ( it needs to be approximately twice as long).
When I discovered this I ( belatedly) realised that I should have put more foresight into the project..! Given that I am unlikely to find an off the peg solution to the Greenspeed axle nor do I have the resources to have a new axle/ kingpin made up - so what to do?
I have noticed that the Greenspeed axle has an internal thread so I did think that I could add an extension to the axle connecting the two parts by an internal screw and thus proceed that way. Is this a mad idea( it seems as if it could work as long as the two pieces of axle were correctly aligned) but maybe I am missing something obvious? If this can’t be made to work I will either have to revert to the previous setup ( and live with my dislike of derailleur gearing) or alternatively use a mid- drive motor at the crank. I had this setup on my KingCycle which worked well but I just think that the Grin AllAxle is a superb motor so I am reluctant to give up quite yet. Any views, help will be gratefully received!

I'm in a similar situation and decided to build my own hub motor with integrated geared hub. Unfortunately, it's going to take a while...
In the meantime, I'd suggest 3 options:
1 - expensive: get 2x front side mounted GAA motors and have a pair of axles machined to your needs.
2 - keep the rear motor and add a torque sensor to your bottom bracket, or a limited throttle. That should help with starts and get rid of the main inconvenient of derailleurs on trikes. You'll still have to clean it though...
3 - if you're crafty, you can build a mount for an internal geared hub that fits the greenspeed main tube. Plenty of space beneath the seat. Then use the IGH as jagshaft for a left side drive, and bolt a cog on the 44bcd mount of the GAA. There is no rear brake anyway on the GT20 and you can still use the motor as e-brake. Use a clamp design to make it adjustable and you're good to go.

 

[amberwolf]

I To this end I have a Grin front All Axle but what I didn’t factor in is that the axle on the Greenspeed is not long enough to accommodate the motor ( it needs to be approximately twice as long).
When I discovered this I ( belatedly) realised that I should have put more foresight into the project..! Given that I am unlikely to find an off the peg solution to the Greenspeed axle nor do I have the resources to have a new axle/ kingpin made up - so what to do?

Is the axle part of the whole "knuckle", or is it threaded into it or bolted to it? I couldn't find specific info or good enough images on the Greenspeed site to tell. You would need to directly contact them to find out details of it's construction that you can't see on the parts you have there. (if you post detailed, high resolution, well-lit, in-focus images, best taken in direct sunlight, of all angles of the relevant parts, we can make better guesses as to how it is made and what you might be able to do).

I have noticed that the Greenspeed axle has an internal thread so I did think that I could add an extension to the axle connecting the two parts by an internal screw and thus proceed that way. Is this a mad idea( it seems as if it could work as long as the two pieces of axle were correctly aligned) but maybe I am missing something obvious?

As long as the parts fit correctly and have no play, it should work ok, as long as the GAA axle internally (ID) fits correctly against the entire length of the outside (OD) of the whole axle, extension and all (the extension must be the same OD as the orignal in this case), with no cavities inside, so that there is no "prying" going on at the outer end of the axle vs the point the extension mounts to the original. The weakness of this method is the stress riser created at the point hte extension decreases in diameter to teh threaded section.


Alternately, if the GAA axle internally (ID) is larger than the orignal, then have your extension made so that it is as long as the entire length required, and it has an internal hollow section that's ID matches the OD of the orignal axle. For this to work the threaded portion that screws into the orignal axle must be separate, or it can't be threaded by the machining process to create the extension. The simplest way is to have a cylinder that is identical to the orignal axle in OD and ID, with identical threading, and use the correct bolt that matches the present wheel-mounting bolt in type, thread, diameter, and strength, but long enough for the new complete assembly.

The same method could be used for a shorter same-diameter extension.


In all cases you'll need the GAA torque arm to correctly mount to the steering knuckle itself, so it must be on the inboard side.

EDIT: The ebikes.ca adapter for greenspeed trikes

 

[offGridDownUnder]

Any views, help will be gratefully received!

How I did it, to date (well, not quite fully up to date):
Greenspeed Magnum Big Wheel with 'stoke monkey' motor and Gates Belt drive

You could, instead, place the Rohloff in the position behind the seat, and carry it's output back to the left side of the Grin All-Axle in the rear. Or, you could put the motor behind the seat and carry it's output back to the left side of the Rohloff. In both of these cases, you will have regen.

Or, you could put the Rohloff in the rear wheel, keep the chain from the front crank along the right side to the Rohloff (largely as it is from the factory), and supplement that with a motor behind the seat connected to the left side of the Rohloff.

In all cases, the power will sum.

I would put the motor behind the seat as then I could tune the "gear" reduction from the motor to the wheel to map the motor output to my desired riding speeds to make best use of the motor over it's range. This is what I am doing now, of course, although I am putting my own pedaling input into the motor via the sprockets and derailleur. I have skewed my use towards pulling heavy loads up hills, so I and my groceries or camping gear and trailer can always get home.

I'm sure some people will get excited and insist that the motor power should be presented to the gear input, but you already have the motor and it's already quite capable of providing all the power you need - I don't see that you would gain any by putting the motor output into the Rohloff - you won't have more total power by doing that. The motor only need go through gears if the motor is not itself strong enough.

On my trike, a 250W (Grin) Shengyi SX2 is capable of pulling me up a 12 degree slope with the reduction I have, and it will still move the trike at speeds faster than I can safely turn - in short, it does all the job I might actually need. My current v3 All-Axle fast wind goes up that slope at 13km/hr if I give it the (un-necessary) power.

I have full regen capability with my arrangement. If you couple the Rohloff and motor by a belt on the left side as I do, you will maintain that as well regardless of which is in front of the other.

I recommend you not couple the Rohloff and motor by a chain drive if you want regen. I consulted with a bicycle shop that supplies many track bike riders, and a chain and sprockets in those conditions does not last long. Gates belts are quite at home with the required tension. If you do want to use a chain to couple them, then I'd say you need to introduce a free wheel and that would not be easy on the left side of those components.

I do have an advantage you will not, regardless. I can switch my rear wheel for a wide rim and fat tires for off-road without paying for two Rohloff hubs or two motors. My rear hub is a standard 135mm OLD "Dirt Jump" hub. The "Dirt Jump" designation means it's optimised for BMX off-road riding - it's sturdier and also has a truncated freehub, which in turn means the spoke flanges are wider than a regular rear hub so the spoke lacing is also sturdier. I simply ignore the freehub - it's not in use for my arrangement. I am contemplating putting a fitting there to permit me to use as a winch for pulling the trike up steep hills off-road, but I haven't progressed with that beyond musing about it.

I suspect your trike does not have the same mounting points mine does, and I don't have one like yours to examine. The solution shown in most of the pictures in my thread is obsolete - it was mounted by a clamp onto the main spine of the trike. It wasn't my idea and it ultimately damaged the trike frame. I designed my own motor frame which attaches to some threaded mounting points that Greenspeed/WizWheels/TerraTrike provides from the factory (Greenspeed was sold when Ian Sims died a few years ago).

I had to cut the center cross member of the seat frame to permit the chain to raise up to meet the sprocket(s) on the motor. I've added some triangular bracing to compensate and spoken to a bicycle builder about making a new seat frame.

I'm currently considering my next redesign to permit folding and more convenient rear tube replacement.

 

[offGridDownUnder]

the GAA axle internally (ID)

The All-Axle v2 has a 20mm ID without adapters. The v3 has a 16mm ID without adapters. Grin gave up the extra mm to permit greater distance between the cables and the brake rotor - compensating for that on my Cruzbike was a significant task, perhaps not a problem with the v3.

Grin supplies adapters for single-side mounting, but there is a concern - the earlier Greenspeeds used internal drum brakes and the mounting adapters attach to disk brake mounts.

My recent Greenspeed Magnum Big Wheel was supplied with disk brakes, but I have not attempted to work out the motor mounting so I can't provide much beyond pointing these issues out.

 

[mmiller50]

Thanks so much for all the responses! Having weighed it all up I was probably overoptimistic to think that I could power my Greenspeed with a front hubmotor and not have to do much modification to make it efficient and safe! So , Occam's Razor-like, I've decided to install a crank motor so I can retain the Rohloff . The now redundant Grin All Axle has already found a new home on the front of my KingCycle- so we will see how that goes!)